This application is related to and claims priority from Japanese Patent Applications No. Hei. 11-27864 filed on Feb. 4, 1999, and No. Hei. 11-315555 filed on Nov. 5, 1999.
1. Field of the Invention
The present invention relates to a vehicle air conditioning apparatus which adjusts temperature of air blown into a passenger compartment by combining a hot water valve for adjusting a flow amount of hot water flowing into a heating heat exchanger and a cool air bypass door for adjusting a cool air amount bypassing the heating heat exchanger.
2. Description of Related Art
In an air mixing method of a conventional air conditioning apparatus described in U.S. Pat. No. 5,893,407, a ratio between an amount of cool air bypassing a heating heat exchanger and an amount of warm air passing through the heating heat exchanger is adjusted by an air mixing door, so that temperature of air blown into a passenger compartment is adjusted.
On the other hand, in a hot-water flow adjustment method, an amount of hot water flowing into a heating heat exchanger is adjusted so that temperature of air blown into the passenger compartment is adjusted. In this hot-water flow adjustment method, because a mixing space for mixing cool air and warm air in the air mixing method and an operation space of the air mixing door are not necessary, a size of an air conditioning case can be reduced. Further, since the mixing space is unnecessary, a flow resistance is reduced, and thereby reducing electrical power consumption of a blower unit and air-blowing noise.
However, in the hot-water flow adjustment method, in a case where the temperature of blown-air is in a low-temperature area (i.e., cooling side area), when a user (passenger) further operates a temperature adjustment operation member of an air conditioning panel toward a low-temperature side, the temperature of blown-air is not immediately reduced even when the flow amount of hot water is reduced by reducing an opening degree of a hot water valve. That is, a change of actual temperature of air blown into the passenger compartment is greatly delayed as compared with a temperature-changing operation of the user. Therefore, a temperature-changing response delay for the user may be caused.
Further, the heating heat exchanger has radiation characteristics that, the temperature of blown air is rapidly increased with an increase of hot-water flow amount in a small flow amount area after the hot water valve is opened, and thereafter, the increase ratio of blown-air temperature relative to the increase of the hot-water flow amount becomes slowly. For continuously accurately adjusting the temperature of air blown into the passenger compartment, a hot water valve for finely adjusting the hot-water flow amount in a small-flow area is necessary. However, when the opening degree of the hot water valve is throttled to a little opening degree, a pressure difference between hot water before flowing into the hot water valve and after flowing through the hot water valve becomes larger, a flow rate of hot water passing through a throttle portion of the hot water valve becomes faster, and water-flowing noise is increased.
In a vehicle air conditioning apparatus described in JP-A-10-226219, during a maximum cooling where a hot water valve is fully closed, a cool air bypass passage is opened by a max-cool door. However, because the max-cool door opens the cool air bypass passage only during the maximum cooling, the temperature of blown-air is not controlled in the other control area. Thus, the same problem described above in the hot-water flow adjustment method may be caused.
In view of the foregoing problems, it is an object of the present invention to provide a vehicle air conditioning apparatus using a hot-water flow adjustment, which accurately adjusts temperature of air blown into a passenger compartment without a minute flow control of hot water.
According to an aspect of the present invention, an air conditioning apparatus for a vehicle includes a heating heat exchanger disposed in an air conditioning case to form a bypass passage through which air bypasses the heating heat exchanger, a hot water valve for adjusting a flow amount of hot water flowing into the heating heat exchanger, and a bypass door for opening and closing the bypass passage. In a first set temperature area where temperature of air blown into the passenger compartment is set to be higher than a predetermined temperature, the bypass door fully closes the bypass passage and temperature of air to be blown into the passenger compartment is adjusted by a hot-water flow adjustment of the hot water valve. On the other hand, in a second set temperature area where the temperature of air blown into the passenger compartment is set to be lower than the predetermined temperature, the temperature of air to be blown into the passenger compartment is adjusted by combining the hot-water flow adjustment of the hot water valve and an air flow adjustment of the bypass door. Thus, in the second set temperature area, the temperature of air blown into the passenger compartment can be accurately adjusted by mixing cool air from the bypass passage into warm air from the heating heat exchanger, even when the flow amount of hot water is not adjusted in minute by the hot water valve in the second set temperature area. As a result, it is unnecessary to set the hot water valve at a minute opening degree, and flow noise of hot water can be greatly reduced. Further, when the temperature of air blown into the passenger compartment is controlled to a low-temperature side, the air temperature is immediately reduced by increasing the amount of cool air from the bypass passage, and therefore, the temperature of air blown into the passenger compartment is immediately changed with a variation in a set temperature.
In the air conditioning apparatus, the hot water valve is fully opened and the bypass door fully closes the bypass passage at a highest-temperature position of an operation member, and the hot water valve is fully closed and the bypass door fully opens the bypass passage at a lowest-temperature position of the operation member. Further, when the operation member operates from the highest-temperature position to a predetermined position between the highest-temperature position and the lowest-temperature position, the hot water valve gradually reduces the flow amount of hot water flowing into the hot water valve while the bypass door maintains at a fully closing state of the bypass passage, and the bypass door increases an opening degree of the bypass passage so that the amount of air passing through the bypass passage is gradually increased when the operation member operates from the predetermined position toward the lowest-temperature position. Thus, heating capacity in a heating operation and cooling capacity in a cooling operation can be sufficiently improved in maximum.
Preferably, when the operation member operates from the lowest-temperature position toward a side of the highest-temperature position, the hot water valve is opened at one step from a fully closed state to a predetermined opening degree where the flow amount of hot water flowing into the heating heat exchanger is equal to or larger than a predetermined flow amount corresponding to 5% of a maximum flow amount due to the hot water valve. Therefore, the flow noise of hot water is effectively reduced.
On the other hand, according to an another aspect of the present invention, an air conditioning apparatus for a vehicle includes an operation member for cooperating the hot water valve and the bypass door, the operation member is operable in an entire operation range between a lowest-temperature position where temperature of air blown into the passenger compartment becomes minimum and a highest-temperature position where the temperature of air blown into the passenger compartment becomes maximum. In a first area from the lowest-temperature position among the entire operation range of the operation member, the temperature of air to be blown into the passenger compartment is adjusted by a hot-water flow adjustment of the hot water valve while the bypass door maintains at a fully opened state where the bypass passage is fully opened. Further, when the operation member operates from the first area to a side of the highest-temperature position, the bypass door reduces the opening degree of the bypass passage from the fully opened state so that the temperature of air to be blown into the passenger compartment is adjusted by combining the hot-water flow adjustment of the hot water valve and an air flow adjustment of the bypass door. Thus, a variation in air temperature due to a variation in hot-water temperature caused with variation in a vehicle engine operation is restricted, and air-conditioning feeling for a passenger in a passenger compartment is improved.
Further, when the temperature of air blown into the passenger compartment is set to be lower than a first predetermined temperature, a face mode where air is blown from a face opening is set, and the temperature of air to be blown into the passenger compartment is adjusted by a hot-water flow adjustment of the hot water valve while the bypass door fully opens the bypass passage during the face mode. When the temperature of air blown into the passenger compartment is set to be higher than a second predetermined temperature higher than the first predetermined temperature, a foot mode where air is blown from the foot opening is set. When the temperature of air blown into the passenger compartment is set between the first and second temperatures, a bi-level mode where air is blown from both the face opening and the foot opening is set. Further, during foot mode and the bi-level mode, an opening degree of the bypass door is reduced from a fully-opened state, and the temperature of air to be blown into the passenger compartment is adjusted by combining the hot-water flow adjustment of the hot water valve and an air amount adjustment of the bypass door. Thus, during the face mode, a temperature changing range of air blown into the passenger compartment is reduced, and air-conditioning feeling is further improved. On the other hand, even during the bi-level mode and the foot mode, the temperature-changing range is reduced as compared with a method where the air temperature is adjusted only by the hot water valve.